Percutaneous interventional procedures to treat occlusive vascular disease, such as angioplasty, atherectomy and stenting, often dislodge material from the vessel walls. This dislodged material, known as emboli, enters the bloodstream, and may be large enough to occlude smaller downstream vessels, potentially blocking blood flow to tissue. The resulting ischemia poses a serious threat to the health or life of a patient if the blockage occurs in critical tissue, such as the heart, lungs, or brain. The deployment of stents and stent-grafts to treat vascular disease, such as aneurysms, also involves introduction of foreign objects into the bloodstream, and also may result in the formation of clots or release of emboli. Such particulate matter, if released into the bloodstream, also may cause infarction or stroke.
Furthermore, interventional procedures may generate foreign bodies that are left within a patient's bloodstream, thereby endangering the life of the patient. Foreign bodies may include, for example, a broken guide wire, pieces of a stent, or pieces of a catheter.
Numerous previously known methods and apparatus have been proposed to reduce complications associated with embolism, release of thrombus, or foreign body material generation. U.S. Pat. No. 5,833,644 to Zadno-Azizi et al., for example, describes the use of a balloon-tipped catheter to temporarily occlude flow through a vessel from which a stenosis is to be removed. Stenotic material removed during a treatment procedure is evacuated from the vessel before the flow of blood is restored. A drawback of such previously known systems, however, is that occlusion of antegrade flow through the vessel may result in damage to the tissue normally fed by the blocked vessel.
U.S. Pat. No. 5,814,064 to Daniel et al. describes an emboli filter system having a radially expandable mesh filter disposed on the distal end of a guide wire. The filter is deployed distal to a region of stenosis, and an interventional device, such as angioplasty balloon or stent delivery system, is advanced along the guide wire. The filter is designed to capture emboli generated during treatment of the stenosis while permitting blood to flow through the filter. Similar filter systems are described in U.S. Pat. No. 4,723,549 to Wholey et al. and U.S. Pat. No. 5,827,324 to Cassell et al.
One disadvantage of radially expandable filter systems such as described in the foregoing patents is the relative complexity of the devices, which typically include several parts. Connecting more than a minimal number of such parts to a guide wire generally increases delivery complications. The ability of the guide wire to negotiate tortuous anatomy is reduced, and the profile of the device in its delivery configuration increases. Consequently, it may be difficult or impossible to use such devices in small diameter vessels, such as are commonly found in the carotid artery and cerebral vasculature. Moreover, such filter devices are generally incapable of preventing material from escaping from the filter during the process of collapsing the filter for removal.
Umbrella-type filter systems, such as described, for example, in U.S. Pat. No. 6,152,946 to Broome et al., also present additional drawbacks. One disadvantage of such systems is that the filters have only a limited range of operating sizes. Accordingly, a number of different filters of different sizes must be available to the clinician to treat different anatomies. Still further, such filters generally do not maintain apposition to the vessel wall when blood pressure pulses pass along a vessel, e.g., due to systole. In this case, because a blood pressure pulse can cause local swelling of the vessel diameter, the pressure pulse can cause the vessel to momentarily become lifted off the perimeter of the filter, thereby permitting emboli to bypass the filter.
International Publication No. WO 98/39053 describes a filter system having an elongated member, a radially expandable hoop and a cone-shaped basket. The hoop is affixed to the elongated member, and the cone-shaped basket is attached to the hoop and the elongated member, so that the hoop forms the mouth of the basket. The filter system includes a specially configured delivery catheter that retains the mouth of the basket in a radially retracted position during delivery.
While the filter system described in the foregoing International Publication reduces the number of components used to deploy the cone-shaped basket, as compared to the umbrella-type filter elements described hereinabove, it too has drawbacks. One such drawback is that because the hoop is fixed directly to the guide wire, the cone-shaped basket may not be fully deployable in a tortuous vessel. This problem is expected to arise, for example, where the resistance of the elongated member to bend to accommodate the tortuosity of the vessel causes the hoop and basket to be lifted away from the vessel wall, thereby providing a path for emboli-laden blood to bypass the filter.
Due to the eccentric nature in which the hoop is fastened to the elongated member in the foregoing International Application, it is expected that the perimeter of the hoop may be lifted away from the vessel wall when devices employing concentric lumens, e.g., angioplasty catheters or stent delivery systems, are brought in proximity of the filter.
Moreover, because the hoop in the aforementioned reference is directly fastened to the elongated member, there is also a risk that the basket will collapse or become wound around the elongated member due to twisting of the elongated member, e.g., during transluminal insertion of the filter, or during manipulation of the proximal end of the elongated member during insertion or withdrawal of interventional devices along the elongated member.
Furthermore, the method for flexibly attaching the filter hoop to the elongated member poses additional challenges. As discussed in the foregoing, if the filter is rigidly affixed directly to the elongated member, then the maneuverability required in accommodating tortuous vessels is compromised. Also, if the filter assembly is not properly attached to the elongated member, then the filter may become disengaged, thereby posing additional risks.
In view of the foregoing disadvantages of previously known apparatus and methods, it would be desirable to provide a vascular device, e.g., for use as a vascular filter, that overcomes such disadvantages and employs few components.